Bad video quality on LCD HDTV/monitor

Alright, so my problem is not so serious, but its really annoying. Everytime i watch a video or DVD on my computer, the quality just isn't there. It's not bad, its just not what it should be. Ive tested the DVDs or other machine and there is a obvious difference. Everytime else looks fine like games and stuff, just not any of my video playback.

Even when i use the monitor as a tv, it works just fine. Im using nothing but my HDMI connection for monitor and t.v.

If anyone know what i could do to improve this , please let me know :]